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Rear diff advice please


s99sdp
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I've got a leak thats getting worse so its time to change the seal on my rear diff. I've found someone to do it, could someone point me in the direction of what I need to order and where from so he's got everything he needs to proceed? It's for my 1970 Mk3 Spit with Overdrive (if that makes any difference)

As always, Many thanks to you all in advance.

 

 

SP

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no the diffs for the small chassis cars are all pretty similar but there are 3 seals, front (most likely to fail) and one each side. The first is the easiest to replace and can be done on the car although of course theres normally no easy way to get the oil out first. The side output shaft seals could possibly be done without removing the diff but are more complicated even though each assembly can be removed to a workbench. You need to identify which is leaking and whether you want to replace all three while your at it.....

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ok and will the diff be removed to do them? Apparently when changing the side seals theres a good chance the bearings will be damaged in the process so the cost of them may have to be factored in.... I must admit I recently took my diff out but did my front seal only as although the sides are originals they do have a much easier life and werent leaking. 

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1 minute ago, johny said:

ok and will the diff be removed to do them? Apparently when changing the side seals theres a good chance the bearings will be damaged in the process so the cost of them may have to be factored in.... I must admit I recently took my diff out but did my front seal only as although the sides are originals they do have a much easier life and werent leaking. 

no idea, would it be best I find out exactly where the leak is first so that if the side seals don't need changing then we just leave them alone?

 

SP

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2 minutes ago, johny said:

I think so and if its only the front seal being done professionally they should be able to get the car up in the air and change it in-situ...

ok cool, is this all I need to order?.........

509137927_Screenshot2020-08-02at14_40_37.png.7771cdbf335b96db8ed13dc1bd9fc567.png

SP

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4 minutes ago, johny said:

it looks like DIFFSET1 includes all three seals and rear gasket whereas if youre only doing the front one you will need just items 29 and 34 

Thanks for that, I'll get on and order it now. 

👍

 

 

SP

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18 minutes ago, thescrapman said:

Have you checked your John gale pin before assuming the seal had gone?

I wont be checking anything scrapman. The guy doing the work has quoted me £75 for the parts so I'm just trying to work out if he's buying them in solid gold format.

I'll take on board your comment, have a read up what it is, where it is and see if I can check it first. thank you for the heads up.

 

I've just a DM exchange with Johny, I think the best thing to do is get under it and see exactly where the leak is coming from first. At that point I can decide what exactly needs to be bought rather than go for the Hail Mary approach.

 

SP

Edited by s99sdp
adding context
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18 minutes ago, thescrapman said:

It is on top of one of the rear mounts, just needs to be loose, if stuck the casing pressurises and forces oil out.

you can see it removing one of the rear wheels, would need to look at a diff to see which one it is

Thank you for that, I'll take a look and see if I can work out what you mean.

👍


SP

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the breather has a split pin in to reduce the hole and keep it clear ,as said gets clogged with oily gunge and road dirt 

it is on the n/s just above /rear of the output shaft casting  best take the N?S wheel off its easy to see through the chassis /body

you cant take the pin out  but a degrease /clean up if its looking clogged 

if you only have a leak from the pinion seal thats all you want to replace ,changing oil seals on the output shafts is not easy 

output shafts dont have gaskets and youre not splitting the case halves so no gaskets are needed , 

pete

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just to add  to change a pinion seal its drop the prop undo coupling nut  pull coupling off  lever out old seal replace new seal refit coupling, torque nut

on youres the nut should be a castle nut and split pin ,  you cant uoset any settings inside the diff , retorque back to where it came from , always turn on to align a split pin not back it off

later cars had a nylock nut and collapsible inner spacer these must be refitted to exactly the same position before removal , or you crush the spacer and that can upset the preloads involved

so castle nut  easy,  nyloc  be careful  you never know whats been changed over the years 

you dont need to drop the diff for any seal replacements  the output shafts with the drive shaft disconnected undo with a hex key through the coupling bolt hols and simply pull out to work on the bench 

getting their bearings off to change the seal is where you run into a fight 

 

Pete

Pete

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  • 1 month later...

Well just to update you, I finally got under the car this weekend and released the pin from 50 years of hurt (gunk, road juice, oil, road kill, ming etc) and its now been freed. 

We have a spare diff here so luckily I located that one under it's own gunk first and saw how it worked. Basically its a split pin with the ends bent over inside that must rise under pressure.

 

Anyway, that said, I'm sure it will end up the seal that leaking 😆

 

Thanks again for all the advice, I'm sure we'll replace the seals on the diff at some point but this little tweak is well worth a try to start with.

SP

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  • 2 weeks later...

Change the front seal first. It’s pretty easy.

If the side seals need doing, it’s more effort as the suspension needs partial dismantling to allow the quarter shafts to be withdrawn. Then, once they are out you have the challenge of getting the bearings off to get at the seals. The bearings will almost certainly be damaged in the process as they are very tightly on the shafts, so get some new ones in.

Nick

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